Addressing reporters in Thiruvananthapuram, state Congress president MM Hassan said the party taking cognisance of the nature of the complaint against Vincent, decided to suspend him from the post of secretary of the party.
However, Mr Hassan said the antecedents of the complainant are being questioned by her own sister.
"The victim's own sister has voiced suspicion about the complainant and her state of mental health. But, as a party that respects womanhood we have decided to suspend him. The question of asking him to resign as a legislator is not going to take place as the case is in the court and we will wait for the outcome of the case," he said.
MM Hassan said the police showed undue haste in acting on the complaint and arresting Vincent.
"This is nothing but a political conspiracy hatched by a CPI-M legislator and leaders of the party. There are quite a few cases of similar nature where CPI-M members are implicated, and in such cases the police did not do anything. But in this case within a few hours Vincent was questioned and then was arrested," said Mr Hassan.
Meanwhile, the sister of the victim on Sunday morning told the media that the victim in the case has been taking medicines for a long time and their brother is a CPI-M activist.
On Saturday, police questioning Vincent for a few hours took him into custody and recorded his arrest. He was later produced before a magistrate, who remanded him to 14 days judicial custody.
This is the first time that a sitting legislator in Kerala has been arrested on such charges.
Vincent had moved for anticipatory bail from a court here, but with his arrest taking place he will now seek bail on Monday.
The woman's husband had filed a complaint with the local police station near here earlier this week accusing the legislator of threatening and harassing his wife over phone.
Vincent, who represents Kovalam Assembly constituency in the state capital district, said he has done no wrong and claimed he was a victim of political conspiracy. He has blamed Chief Minister Pinarayi Vijayan's office for framing him.
The case surfaced after the woman attempted suicide by consuming excessive dose of sleeping pills on Wednesday. She was rushed to a hospital in the city suburbs and was saved.
The police have taken the statement of the woman.
The woman told the media on Saturday that she has been facing severe mental harassment from the legislator and he has misbehaved with her on two different occasions.